nvestigative procedure
• Not emit alpha or beta radiation, because these particles would be trapped in the patient's tissues and not be detected externally
• Emit gamma radiation of an energy which will allow its origin to be efficiently assessed
• Be available in the highest possible specific activity, so that it will not invoke either a toxic or pharmacological response in the patient.
On the other hand, in THERAPEUTIC nuclear medicine, a different set of criteria applies: -
• The half life should not be the cause of an extended stay in hospital for the patient
• The radioisotope should emit particulate (alpha or beta) radiation of sufficient energy to penetrate to all parts of the lesion
• It should, in addition, emit gamma rays to facilitate the assessment that the appropriate region of the body has been targeted.
When a radioisotope is designed for use in a medical application, it is usual for it to be presented in a form, which directs in which part of the body it will concentrate.
This type of presentation is usually referred to as a RADIOPHARMACEUTICAL.
One particular radioisotope may be presented in a number of active forms, each designed to target specific tissues in the human body.
A radiopharmaceutical is the end product of extensive chemical processing of a substance after it has been irradiated in a cyclotron or nuclear reactor.
Most commonly, the preparation of a radiopharmaceutical involves: -
• Extracting the radioisotope from the bulk of the target substance
• Purification from undesirable chemical and radio isotopic impurities
• Chemical conversion to a biologically specific form (may be more than one active form, each targeting specific groups of tissues in the human body)
• Making the preparation suitable for administration to patients
• Testing the quality of the final product.
The most common manufacture of...